Abstract
The dilithio derivatives of N-monosubstituted propanamides are formed as a mixture of stereoisomers in which the Z (O)-isomer is significantly favored by the reaction between the amide and butyllithium in THF-Et2 O at 0 °C. Addition of the dilithio compound to aldehydes results in a mixture of the syn and anti aldols in near equal quantities, and in the recovery of up to 30% of the unreacted amide. The reaction outcome is essentially unaffected by time and temperature. Added zinc chloride changes the isomer ratio, but reduces chemical yields dramatically. The results are interpreted in terms of addition through three isomeric Zimmerman-Traxler-type transition states.
Key Words
aldol addition - dianions - stereochemistry - anilides - amides
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